The N-terminal and C-terminal amino acid sequence of calf rennin

Abstract

The enzyme rennin (EC 3 . 4 . 4 . 3) is well known as the milk clotting enzyme from the fourth stomach of the calf. It appears, however, that the enzyme may be regarded as a suitable model enzyme for studies of the structure and function of gastric proteases. The general properties of the enzyme have recently been reviewed (Foltmann 1966), and the amino acid sequences of some soluble tryptic peptides and the disulphide bridges have been investigated (Foltmann & Hartley 1967). In the latter paper the only soluble tryptic peptides that were investigated were basic or neutral. Subsequent experiments have shown that two acidic peptides, which only appeared with a modest ninhydrin reaction in the first experiments are in fact significant fractions of the tryptic digest. One of these peptides represents the N-terminal amino acid sequence, while the other is a part of the C-terminal amino acid sequence.